Confused about Distributor Vacuum Vent lines

[ZGjethro]

Raddox, what have you found out?

[8543bob]

GOOD MORNING, After I rebuilt my engine I ran her for a week or two without any vent lines. It made no difference. these are vent lines and should have no affect on performance. I think Sal may have hit it on the head.
bob

[MSeriesRebuild]

GOOD MORNING, After I rebuilt my engine I ran her for a week or two without any vent lines. It made no difference. these are vent lines and should have no affect on performance. I think Sal may have hit it on the head.
bob

Truth and consequence.

Vent lines alone do not affect performance in that they have nothing to do with the engine starting and running, BUT, FACT, the lack of ventilation in a sealed distributor with coil enclosed will kill your coil quickly from over heating. If you ran your engine much at all within that period that your lines were not in place, you likely have shortened the overall life of your coil, even though yours didn't die during that time. I wouldn't be surprised if it is producing a somewhat weakened spark today because of being subjected to that heat stress. Please understand I'm not telling anyone what to do to their engine; that is each individuals call. I'm just stating facts that I've seen and learned over many years.

[ZGjethro]

I have both of the distributor lines hooked up, with kind of proper carb fittings. I hear a strong hissing sound at the drivers seat at a certain range of throttle at about half throttle. I don't think I am hearing the intake, but it is possible that I am. I am running a K&N filter, and they hiss a bit. Do other trucks have a his on acceleration or deceleration?

[Carter]

I hear a strong hissing sound at the drivers seat..... Do other trucks have a his on acceleration or deceleration?

Over the past 40+ years I have owned 5 running M 37s with stock air filters and none have ever hissed, your K&N filter is likely to be what causes you to hear the hiss that you do but it could also be a vacuum leak from a loose connection or bad gasket somewhere in the intake system.

[Tuko]

Check your windshield wipers too, my passenger side was hissing

[ZGjethro]

I have yanked all the vacuum lines associated with the manifold and the fuel pump. Wipers are electric now. I have the two lines to the distributor, and the oil fill tube vent hooked up at the elbow. The truck was missing the gas tank and brake vent lines when I bought it, and all holes are plugged. I might go pop the hood and rev the motor a bit.

[ZGjethro]

Please ignore my post above. I went to the truck and gave it full throttle with the hood open. The K&N almost whistles for a second with a sudden throttle opening.

[RADDOX]

Ok sorry for the delay but work seems to think
Building a hiway is a priority ! Anyway I tore into
The distributor and could see that the points were not
Making a visible break. Readjusted and bang away
She goes. All I can figure is it was grounding out when
I moved that line against the block. Got me but
It no longer effects it and she's back making tracks and
Getting looks !